* {
  margin: 0;
  padding: 0;
  list-style: none;
  text-decoration: none;
  box-sizing: border-box;
}

html, body {
  width: 100%;
  height: 100%;
}

body {
  display: flex;
  flex-direction: column;
}

body header, body #tab {
  width: 100%;
  height: 50px;
  border-bottom: 1px solid #ccc;
}

body header #tab, body #tab #tab {
  display: flex;
}

body header #tab li, body #tab #tab li {
  flex: 1;
  text-align: center;
  line-height: 50px;
}

body main {
  flex: 1;
}

.active {
  color: red;
}
